1. Field of the Invention
The present invention relates to a toothed-wheel gear with parallel shafts with load branching, having a driving shaft with a driving wheel which meshes with intermediate wheels of two intermediate shafts, the latter driving directly by means of pinions or over further intermediate shafts a power shaft.
2. Description of the Prior Art
Gears with load or power branching are preferably provided where a high power density, low weight and small sizes are asked for. Classic solutions are planetary gears in which the total power to be transmitted is distributed on at least three meshing teeth. However, for a great number of applications such a planetary gear is no longer suitable, such as for extreme high-speed gears with high power or for marine gears requiring a high degree of quietness.
For such type of applications toothed-wheel gears with parallel shafts are e.g. constructed having a double power branching. In such gears a driving wheel is driving, by means of two intermediate wheels, a common power wheel whereby the driving power is divided on the two teeth meshings with said intermediate wheels. Such gears may be constructed as multistage gears using the same principle. The basic problem in gears of this type is to distribute the total power uniformly, i.e. by 50% each on the two power paths. However, due to manufacturing tolerances in the toothings, the shafts and the bearings, as well as misalignment of shafts and thermal deformations during operation, the required power distribution could only be reached accidentally if no appropriate supplementary measures are taken. As the stiffness of each individual tooth meshing is much too great to be able to compensate the described influences, such gears need constructive corrections in order to reach a uniform power distribution.
The standard solution in two-stage gears, as mainly in use in marine vehicles with turbine drive, consists in the connection of the intermediate wheels of the first stage with the pinions of the second stage by means of torsion-elastic torsion shafts. However, such a construction asks for four radial bearings for each intermediate shaft, hollow wheels and pinions, as well as a torsion shaft and, at least in the case of a herringbone gearing (double helical gearing) an additional axially yielding element. Such a solution is therefore quite complicated and expensive.
An other solution is e.g. described in DE-A-2363 968. In this known construction, the driving wheel is provided with adjusting means comprising movably supported bearings of the driving wheel. The mobility or flexibility required is achieved by means of a swivel arm, tilting or sliding shoes or by an appropriate arrangement of a radial tilting segment bearing. This asks in any case for an additional constructional expenditure. Furthermore, there appear, in operation, restoring forces which produce in the moving mechanism frictional forces. These known expensive solutions can be used for single or multi-stage gears.